It is known from U.S. Pat. No. 2,881,052 to form chlorine dioxide by the reduction of an acid aqueous chlorate solution using methanol. However, the reaction involved is quite slow, requiring a time-consuming operation in a succession of reactors and results in a large volume of liquid effluent containing sulphuric acid, unreacted sodium chlorate and sodium sulphate by-product. The efficiency of conversion of chlorate to chlorine dioxide is quite low, generally not exceeding about 90%. Air typically is passed into the reaction medium to dilute the chlorine dioxide.
The overall reaction involved in this prior art process, known commonly as the "Solvay" process, may be represented by the equation: EQU 2NaClO.sub.3 + 2H.sub.2 SO.sub.4 + CH.sub.3 OH.fwdarw.2ClO.sub.2 + 2NaHSO.sub.4 + HCHO + 2H.sub.2 O (1)